All spell casters gain their abilities through a form of demon possession. So in order to gain magical abilites, PCs must track down and trap demons. Of course there are some pretty powerful demons, if the demon is stronger than the PC, the PC could find themselves subjugated to the Demon's will.
The king's palace is destroyed by a falling star, which detonates like a nuclear bomb in the center of the city. When the inhabitants grow brave enough to investigate the ruins of the palace, they find a new ruler, one from beyond the stars, emerging from the meteor.